1. Field of the Invention
The present invention relates to a vehicle control apparatus for controlling a driving force to be given to a vehicle.
2. Description of the Related Art
There is a conventional technology of controlling a driving force or a braking force, which is given to a vehicle, in order to set a vehicle speed to a desired speed (target speed). For example, Japanese Patent Application Laid Open NO. 2004-90679 discloses a technology in which an amount of increasing the driving force is increased more as a deviation between the vehicle speed and the target speed becomes larger, on a drive control apparatus for controlling the driving force (or driving torque) so as to make the vehicle speed close to the target speed.
Moreover, there is also a conventionally known technology of controlling the driving torque (or driving force) and breaking torque (breaking force) when the vehicle runs on a slope or the like. For example, the above-mentioned Japanese Patent Application Laid Open NO. 2004-90679 discloses a creep drive control apparatus on which gain for determining an increasing rate per unit time of the driving torque, which is given to the vehicle, is set to have an optimum value, on the basis of feedback control (automatic control) in which the deviation between the vehicle speed and the target speed is an input value and on which the vehicle speed is controlled in a constant range.
However, in the above-mentioned Japanese Patent Application Laid Open NO. 2004-90679, considering the case where the vehicle runs at a low speed (or extremely low speed), such as off road running, for example, driving forward over a bump from the stop condition that the vehicle stops in contact with the bump, requires the larger driving torque in a moment, though the gain for increasing the driving torque is set at a low level because the target speed is low and thus the deviation is small. Thus, there are such technical problems that it takes a long time for the vehicle to make the driving torque reach the driving torque required to drive forward over the bump, and that a driver feels something is wrong and misunderstands it is a failure.
In other words, in the technique described in the above-mentioned Japanese Patent Application Laid Open NO. 2004-90679, it takes a time to run over the bump if the vehicle stops on the bump or the like, in some cases. This is because if the target speed is set to be relatively low when the vehicle stops on the bump or the like, the small deviation between the vehicle speed and the target speed reduces the amount of increasing the driving force.